As it is programs have to guess the following;
A) encoding. If ANSI which code page? If unicode which encoding? In the case of utf-16 big or little endian?
B) line endings? CR? LF? CRLF? I guess no-one uses LFCR... right?
C) number formats? 100.000 or 100,000? Date formats? is that mm-dd-yyyy or dd-mm-yyyy?
D) what human-language is it in?
E) CSV? Don't get me started...
Yes. Text is a lot easier to load, parse, make guesses about than say XLS. Yes all of the above things can be "guessed" to a greater or lesser extent.
Yes BOM exists to at least try solving the encoding question. Of course most files don't use them. Lots of tools don't support them. And they don't solve any of the other issues.
But sure, ASCII files in English with US date formats, and Windows line endings....no problems at all...